We present a study using a method able to assess tissue oxygenation, taking into account the absorption and the level of scattering in myocardial tissue using a calibrated fiber optic probe. With this method, interindividual comparisons of oxygenation can be made despite varying tissue optical properties during coronary artery bypass grafting (CABG). During CABG, there are needs for methods allowing continuous monitoring and prediction of the metabolism in the myocardial tissue. 14 patients undergoing CABG are investigated for tissue oxygenation during different surgical phases using a handheld fiber optic spectroscopic probe with a source-detector distance of less than 1 mm. The probe is calibrated using a light transport model, relating the absorption and reduced scattering coefficients (µa and µ) to the measured spectra. By solving the inverse problem, absolute measures of tissue oxygenation are evaluated by the sum of oxygenized hemoglobin and myoglobin. Agreement between the model and measurements is obtained with an average correlation coefficient R2 of 0.96. Oxygenation is found to be significantly elevated after aorta cross-clamping and cardioplegic infusion, as well as after reperfusion, compared to a baseline (p<0.05). Tissue oxygenation decreases during cardiac arrest and increases after reperfusion.
In vivo diagnostics of skin diseases as well as understanding of the skin biology constitute a field demanding
characterization of physiological and anatomical parameters. Biomedical optics has been successfully used, to
qualitatively and quantitatively estimate the microcirculatory conditions of superficial skin. Capillaroscopy, laser
Doppler techniques and spectroscopy, all elucidate different aspects of microcirculation, e.g. capillary anatomy and
distribution, tissue perfusion and hemoglobin oxygenation. We demonstrate the use of a diffuse reflectance hyperspectral
imaging system for spatial and temporal characterization of tissue oxygenation, important to skin viability. The system
comprises: light source, liquid crystal tunable filter, camera objective, CCD camera, and the decomposition of the
spectral signature into relative amounts of oxy- and deoxygenized hemoglobin as well as melanin in every pixel resulting
in tissue chromophore images. To validate the system, we used a phototesting model, creating a graded inflammatory
response of a known geometry, in order to evaluate the ability to register spatially resolved reflectance spectra. The
obtained results demonstrate the possibility to describe the UV inflammatory response by calculating the change in tissue
oxygen level, intimately connected to a tissue's metabolism. Preliminary results on the estimation of melanin content are
also presented.
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